In the field of biometric sensors, such as fingerprint sensors, efforts are made to fool of “spoof” an image sensor/collector and image producing system and method, e.g., by forming a fake finger, such as out of a material like so-called “silly putty” and forming on the fake finger an image of a fingerprint in an effort to falsely obtain access to an electronic device protected by a biometric image sensor and comparison system and method. There exists in the art a need for a system and method for authenticating that the biometric object being imaged for comparison is, in fact, part of a human body from which the biometric sensor is detecting the image.
One example of a fingerprint swipe sensor is described in U.S. Pat. No. 6,289,114 entitled FINGERPRINT-READING SYSTEM. This patent describes a system in which the surface area of the sensor is far smaller than the surface area of the fingerprint to be read. The reading is done when the sensor and the finger are in contact and in a relative motion of sliding of the sensor and the finger with respect to each other. The system reconstitutes a complete image of the fingerprint from the partial images given by the sensor during this motion, utilizing pressure and/or temperature from the finger being sensed. The manner in which the system reconstitutes a complete image of the fingerprint from the partial images given by the sensor is not described. Another example of a swiped sensor utilizing capacitive coupling through features of the biometric being imaged, e.g., fingerprint ridges and valleys can be found in U.S. Pat. No. 7,099,496, entitled SWIPED APERTURE CAPACITIVE FINGERPRINT SENSING SYSTEMS AND METHODS.
As discussed in U.S. Pat. No. 5,940,526 to Setlak et al., issued on Aug. 17, 1999, entitled, ELECTRIC FIELD FINGERPRINT SENSOR HAVING ENHANCED FEATURES AND RELATED METHODS, an integrated circuit fingerprint sensor including an array of RF sensing electrodes can provide an image of the fingerprint ridges and valleys. The RF sensing permits imaging of live tissue, including just below the surface of the skin, and in that sense itself is a primative form of reducing spoofing. Setlak et al. is incorporated herein by reference.